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Scientists have discovered that two of the key coral species comprising Florida's reef are now ecologically extinct following a withering ocean heatwave caused devastating losses.

What 'Functional Extinction' Signifies

The near-total collapse of these corals, which once formed the foundation of reefs in Florida and the Caribbean, means they can no longer fulfill their previously crucial role in constructing and maintaining reef ecosystems that support a variety of marine life.

Functional extinction is a phase before global extinction, a danger that now looms for many coral species.

Researchers this month warned that a tipping point had been reached, meaning corals globally are likely to be eradicated due to global heating, which is increasing ocean temperatures to unbearable levels.

Expert Perspective

"We're running out of time," stated Ross Cunning of the new Florida study. "Severe marine heatwaves are increasing in frequency and severity due to climate change, and without swift, decisive measures to reduce ocean heating and enhance coral survival, we risk the extinction of even more corals from reefs in Florida and worldwide."

Details of the Recent Study

The recent study, published in the Science journal, analyzed the outcome of staghorn and elkhorn corals off the Florida coast after a intense marine heatwave in 2023.

This event elevated temperatures on Florida's deteriorating coral reefs to their highest levels in more than a century and a half.

The two species are intricate, reef-forming corals and are named because they look like, respectively, the antlers of male deer and elks.

However, researchers who performed underwater surveys of more than 52,000 colonies of the species, across nearly four hundred sites along Florida's coast, found widespread, often devastating, losses.

Regional Impact

• In the Florida Keys, mortality rates reached 98% and even 100%, revealing a total eradication of the corals.
• In south-east Florida, where temperatures have been lower, death rates were reduced, at about thirty-eight percent.

Historical and Present Dangers

The two Acropora species had already endured from decades of localized impacts in Florida, such as contaminated water from contaminants that wash off the land, as well as illness.

But the 2023 heatwave has been lethal for these heat-sensitive species.

The 2023 heat event caused the ninth episode of coral bleaching on the Florida reef – a process whereby corals become heat-stressed and expel the algae partners living in their tissues, causing them to become ghostly white.

If temperatures remain elevated, the corals perish entirely.

Worldwide Consequences

Globally, coral reefs are among the ecosystems most vulnerable to the anthropogenic climate crisis.

This poses a major threat to:

• A quarter of all ocean life that relies upon what are effectively the rainforests of the sea.
• Hundreds of millions of people who depend upon corals to sustain fish that they can consume and gain an income from.

Corals also serve as a protective barrier to protect our shorelines from powerful storms, which are themselves being intensified by rising global temperatures.

Preservation Efforts

In a last-ditch effort to prevent a decline of endangered corals, scientists have created collections of Acropora in marine facilities and offshore coral nurseries.

Efforts have been made to replant corals on reefs in Florida, as well, in an effort to regain some of the 90% of coral cover disappeared off the state in the past four decades.

But as global heating continues to intensify, there is slim chance of continued existence of these species without major interventions, researchers warn.

Further Researcher Insight

"Elkhorn corals, in particular, are some of the most important wave-dampening coral species in the area," said Andrew Baker, a marine biologist at the University of Miami.

"They used to be abundant on shallow reef crests in the Caribbean, and if we want our reefs to keep safeguarding our coastlines from flooding during storms, it is worthwhile taking exceptional steps to ensure we don't lose these corals completely."